You have 2 different ways of installing courier-auth-postfix. The first one should work on any system or any distribution, and involves getting the source from www.postfix.org and compiling it. The second one consists in installing the .deb packages on any debian distribution. You should find at least one method that suits your needs. The debian packages used to be available on my own site, but they are now available upon request. If you need them, just mail me... I'll send you either precompiled binaries or a patch to build the debian packages.
Note, however, that since courier-auth-postfix is linked against some libraries provided with postfix, you must have installed the same version of postfix you used to compile courier-authpostfix with.